California is set to require solar panels on all newly built single-family houses, the first statewide mandate in the nation. That's expected to save buyers money in the long run, but will raise their upfront costs at a time many are already struggling to afford a mortgage.

The Belridge oil field in the San Joaquin Valley of California has produced about 1.7 billion barrels of heavy crude since its discovery in 1911. Thanks to advances in solar power, its next 500 million barrels will be a little bit greener.

President Trump’s most useful ally in his push to restore the dominance of coal, oil and gas in America could ultimately turn out to be a pair of bankrupt solar firms seeking help from the federal government getting back on their feet.